Method for navigating an automated guided vehicle

ABSTRACT

A method for navigating an automated guided vehicle is provided. The method includes: generating an environment map for an automated guided vehicle and setting a target position, wherein the environment map at least includes an open region and a barrier region; generating a first navigation path on the environment map according to the target position; optimizing the first navigation path by using a dichotomy method to generate a second navigation path; orthogonalizing the second navigation path to generate a third navigation path, wherein every two adjacent line segments in the third navigation path are orthogonal to each other; and navigating the automated guided vehicle to the target position using the third navigation path. The method for navigating the automated guided vehicle according to the invention optimizes navigation paths.

This application claims the benefit of People's Republic of Chinaapplication Serial No. 201611089135.5, filed Nov. 30, 2016, the subjectmatter of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION Field of the Invention

The invention relates in general to a field of automatic control, andmore particularly to a method for navigating an automated guidedvehicle.

Description of the Related Art

AGV, which stands for “Automated guided vehicle”, refers to a vehicleequipped with an electromagnetic automatic guiding device or an opticalautomatic guiding device. The AGV can drive along a planned guiding pathand provide safety protection and various transfer functions.

Currently, the path planning of an AGV is mainly based on safety anddistance. However, since the environment map obtained using simultaneouslocalization and mapping (SLAM) technology has serrations, at which theplanned path needs to change direction frequently, the AGV also needs tochange direction frequently when following the planned path.

Due to technological limitations and the influence of scanningfrequency, when a radar scanner used in an AGV scans the surroundingenvironment, the generated environment map will contain noises and haveuneven edges. If path planning and navigation is based on such a crudemap, the AGV will not be stable safety concern will arise when the AGVtravels on the road.

SUMMARY OF THE INVENTION

To resolve the defects of the prior art, the invention provides a methodfor navigating an automated guided vehicle, capable of optimizingnavigation paths of the automated guided vehicle.

According to one embodiment of the present invention, a method fornavigating an automated guided vehicle is provided. The method includes:generating an environment map for the automated guided vehicle andsetting a target position, wherein the environment map at least includesan open region and a barrier region; optimizing the first navigationpath by using a dichotomy method to generate a first navigation path onthe environment map according to the target position; generating asecond navigation path; orthogonalizing the second navigation path togenerate a third navigation path, wherein every two adjacent linesegments in the third navigation path are orthogonal to each other; andnavigating the AGV to the target position using the third navigationpath. The above and other aspects of the invention will become betterunderstood with regard to the following detailed description of thepreferred but non-limiting embodiment(s). The following description ismade with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flowchart of a method for navigating an AGV according to anembodiment of the invention.

FIG. 2 is a schematic diagram of an environment map according to anembodiment of the invention.

FIG. 3 is a schematic diagram of an environment map having a bufferregion according to an embodiment of the invention.

FIG. 4 is a schematic diagram of the Dijkstra's algorithm according toan embodiment of the invention.

FIG. 5 is a schematic diagram of a first navigation path according to anembodiment of the invention.

FIG. 6 is a schematic diagram of a second navigation path according toan embodiment of the invention.

FIG. 7 is a schematic diagram of a third navigation path according to anembodiment of the invention.

FIG. 8 is a schematic diagram of a pre-optimized environment mapaccording to an embodiment of the invention.

FIG. 9 is a schematic diagram of an optimized environment map accordingto an embodiment of the invention.

FIG. 10 is a schematic diagram of a barrier region according to anembodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

Detailed descriptions of exemplary embodiments of the invention aredisclosed below with accompanying drawings. However, exemplaryembodiments can be implemented in many different ways, and should beunderstood as being limited to the embodiments disclosed below. On thecontrary, the descriptions of the exemplary embodiments are forcompletely transferring the concepts of the exemplary embodiments totechnical personnel of the technology field of the invention.Designations common to the accompanying drawings are used to indicateidentical or similar elements, and repetitions in the descriptions ofidentical or similar elements are omitted.

Accompanying drawings of the invention are merely used to illustraterelative positions of the components, and the sizes of the componentsillustrated in the accompanying drawings are not based on actual scales.Detailed descriptions of the method for navigating the AGV according tothe invention are disclosed below with reference to accompanyingdrawings.

Referring to FIG. 1, a flowchart of a method for navigating an AGVaccording to an embodiment of the invention is shown. As illustrated inFIG. 1, the method includes 5 steps. In step S110: an environment map201 for an automated guided vehicle (AGV) is generated and a targetposition is set.

Referring to FIG. 2, a schematic diagram of an environment map accordingto an embodiment of the invention is shown. The environment map 201 atleast includes an open region 211 displayed in white color and a barrierregion 212 displayed in black color. The environment map 201 may furtherinclude an un-explored region 213 displayed in gray color. Optionally,during travelling, the laser scanner installed in the AGV continuouslyrotates to explore the surrounding environment, and further performspositioning to generate an environment map 201 according to the scanneddata using the SLAM technology.

Optionally, in step S110, the environment map 201 is optimized.Referring to FIG. 3, a schematic diagram of an environment map having abuffer region according to an embodiment of the invention is shown. Theoptimization step includes: using the open region within a distance tothe edge of the barrier region 212 as a buffer region 214. The bufferregion 214 is regarded as a barrier region in subsequent steps ofgenerating a navigation path and optimizing the navigation path. Someother optimization steps are described below with reference to FIG. 8 toFIG. 10.

In step S120: a first navigation path 210 is generated on theenvironment map 201 according to the target position. Optionally, thefirst navigation path 210 can be generated using the Dijkstra'salgorithm. Details of the Dijkstra's algorithm can be obtained withreference to FIG. 4. Referring to FIG. 4, a schematic diagram of theDijkstra's algorithm according to an embodiment of the invention isshown. Set pixel point be the unit used in the environment map 201.Starting from the target position 222, weights are assigned to the eightpixel points surrounding the target position 222. The four pixel pointsrespectively located on the top, the bottom, the left and the right ofthe target position 222 have the same weight, for example, a weight of10, and the four pixel points located on the two diagonal lines of thetarget position 222 have the same weight, for example, a weight of 14.The weight of the four pixel points on the two diagonal lines is greaterthan the weight of the four pixel points located on the top, the bottom,the left and the right of the target position 222. Set the pixel pointwhose surrounding pixel points have been weighted be used as a referencenode. Then, the eight pixel points surrounding the reference node areweighted, for example, the weighting method is similar to that of theeight pixel points surrounding the target position 222, until thestarting node 221 of the AGV is weighted. Starting from the startingnode 221 of the AGV, the pixel point whose weight has a largestdifference with that of the starting node 221 is selected as the currentpixel point, for example, the pixel point in FIG. 4 having a weight of28 and being adjacent to the starting node 221 is selected. Then,starting from the current pixel point, another pixel point whose weighthas a largest difference with that of the current pixel point isselected and used as the next pixel point, and the selection procedureis repeated until the target position 222 is selected. The connectionline connecting the starting node 221 and the target position 222 ofFIG. 4 is used as the first navigation path 210.

Referring to FIG. 5, a schematic diagram of a first navigation pathaccording to an embodiment of the invention is shown. The firstnavigation path 210 of the environment map 201 generated by using theDijkstra's algorithm can be obtained with reference to FIG. 5. The firstnavigation path 210 includes a plurality of first navigation nodesa₀˜a_(n−1). The first navigation nodes a₀˜a_(n−1) form a firstnavigation node set S1={a₀, a₁, a₂ a_(n−1)}, wherein n is an integergreater than or equal to 1. When n=9, it means the first navigation path210 includes 9 first navigation nodes a₀˜a₈, which form the firstnavigation node set S1={a₀, a₁, a₂ . . . a₈}.

In step S130: the first navigation path 210 is optimized by using adichotomy method to generate a second navigation path 220. Specifically,in step S130, two first navigation nodes are selected using a dichotomymethod, and whether the connection line connecting the two firstnavigation nodes passes through the barrier region, such as the barrierregion 212 and the buffer region 214, is determined, and a plurality ofsecond navigation nodes and a plurality of second navigation nodes areselected from a plurality of first navigation nodes to form the secondnavigation path, wherein the quantity of second navigation nodes issmaller than or equal to the quantity of first navigation nodes.

In a specific embodiment, step S130 can be implemented using followingalgorithm: (1) Set k1=0, k2=n−1. (2) Set A=a_(k1), B=a_(k2), whereinnodes A and B are two nodes selected from the first navigation node set,and k1 and k2 respectively indicate the two first navigation nodes inthe first navigation node set that correspond to the nodes A and B. (3)Determine whether the line segment formed by the nodes A and B passesthrough the barrier region, such as the barrier region 212 and thebuffer region 214. If the line segment formed by the nodes A and Bpasses through the barrier region, such as the barrier region 212 andthe buffer region 214, set k2=(k1+k2)/2 and round k2, and the methodreturns to step (2). If the line segment formed by the nodes A and doesnot pass through the barrier region, such as the barrier region 212 andthe buffer region 214, and k2≠n−1, the node A is used as a secondnavigation node and is added to the second navigation node set S2, setk1=k2, k2=n−1, and the method returns to step (2). If the line segmentformed by the nodes A and B does not pass through the barrier region,such as the barrier region 212 and the buffer region 214, and k2=n−1,the nodes A and B are used as second navigation nodes and are added tothe second navigation node set S2. (4) Obtain the second navigation nodeset S2, wherein a plurality of second navigation nodes in the secondnavigation node set S2 form the second navigation path.

The algorithm is described below using FIG. 5 as an example: Set k1=0,k2=8. Set A=a0, B=a8. Whether the line segment formed by the node A (a₀)and the node B (a₈) passes through the barrier region, such as thebarrier region 212 and the buffer region 214, is determined. Setk2=(k1+k2)/2=4. Whether the line segment formed by the node A (a₀) andthe node B (a₄) passes through the barrier region, such as the barrierregion 212 and the buffer region 214, continues to be determined. Setk2=(k1+k2)/2=2. If the line segment formed by the node A (a₀) and thenode B (a₂) does not pass through the barrier region, such as thebarrier region 212 and the buffer region 214, and k2≠8, the node A (a₀)is used as a second navigation node and is added to the secondnavigation node set S2, and set k1=k2=2, k2=8. Based on the subscript,whether the connection line connecting the nodes A and B passes throughthe barrier region, such as the barrier region 212 and the buffer region214, is determined according to the above method to select new secondnavigation nodes. For example, in the present embodiment, the firstnavigation nodes a₀, a₂, a₄, a₅, a₆, a₈ are selected according to thealgorithm and are used as the second navigation nodes to form the secondnavigation node set, and the second navigation path is formed. It can beseen that through step S130, the quantity of navigation paths and thequantity of navigation nodes can be effectively reduced.

Referring to FIG. 6, a schematic diagram of a second navigation pathaccording to an embodiment of the invention is shown. Specifically, aplurality of second navigation nodes b_(0˜)b_(m−1) are selected from aplurality of first navigation nodes to form the second navigation nodeset S2={b₀, b₁, b₂ . . . b_(m−1)}, wherein m is an integer greater thanor equal to 1. A plurality of second navigation nodes b₀˜b_(m−1) formthe second navigation path 220, as indicated in FIG. 6. In the presentembodiment, m=6, the second navigation path 220 includes 6 secondnavigation nodes b₀˜b₅.

In step S140: The second navigation path 220 is orthogonalized togenerate a third navigation path 230. Referring to FIG. 7, a schematicdiagram of a third navigation path according to an embodiment of theinvention is shown. As indicated in FIG. 7, every two adjacent linesegments in the third navigation path 230 are orthogonal to each other.Specifically, in step S140, an additional node is formed with respect toevery two adjacent second navigation nodes, wherein the connection linesconnecting the additional node and the two adjacent second navigationnodes are parallel to the X direction, that is, the first direction, orthe Y direction, that is, the second direction, and the X direction isperpendicular to the Y direction; and the additional node and at leastsome of the second navigation nodes are used as third navigation nodes,wherein a plurality of third navigation nodes form the third navigationpath 230.

In a specific embodiment, each of the second and third navigation nodeshas a horizontal coordinate along the X direction, that is, the firstcoordinate, and a vertical coordinate along the Y direction, that is,the second coordinate, and step S140 can be implemented using followingalgorithm: (1′) Set j1=0, j2=1, designation variable p=0, and thequantity of second navigation nodes in the second navigation node set S2be denoted by q. (2′) Set C=b_(j1), D=b_(j2), wherein nodes C and D aretwo nodes selected from the second navigation node set, and j1 and j2respectively indicate the two second navigation nodes in the secondnavigation node set that correspond to the nodes C and D. (3′) Set thefirst coordinate of the additional node be the first coordinate of thenode C, and the second coordinate of the additional node be the secondcoordinate of the node D. (4′) Respectively determine whether the linesegments formed by the nodes C and D and the additional node passthrough the barrier region.

If the line segments formed by the nodes C and D and the additional nodeboth do not pass through the barrier region, and j2≠m−1, the node C andthe additional node are used as third navigation nodes and are added tothe third navigation node set S3, set j1=j1+1, j2=j2+1, and the methodreturns to step (2′). If j2=m−1, the nodes C and D and the additionalnode add are used as third navigation nodes and are added to the thirdnavigation node set S3; If at least one of the line segment formed bythe nodes C and D and the additional node passes through the barrierregion, set p=p+1.

When p=1, set the first coordinate add.x of the additional node add isthe first coordinate D.x of the node D, the second coordinate add.y ofthe additional node add is the second coordinate C.y of the node C, andthe method returns to step (4′). When p=2, set b_(q)=b_(q−1),b_(q−1)=b_(q−2) . . . b_(j2+1)=b_(j2), b_(j2).x=(C.x+D.x)/2,b_(j2).y=(C.y+D.y)/2, q=q+1, p=0, and the method returns to step (3′).(5′) Obtain the third navigation node set S3, wherein the thirdnavigation nodes in S3 form the third navigation path.

The algorithm is described below using FIG. 6 as an example: Set j1=0,j2=1, designation variable p=0, the quantity of second navigation nodesin S2 be denoted by q. Set C=b₀, D=b₁, the X coordinate add.x of theadditional node add be the X coordinate add.x of the node C, and the Ycoordinate add.y of the additional node add be the Y coordinate D.y ofthe node D. Thus, the additional node add1 is obtained. If the linesegment formed by the node C and the additional node add1 and the linesegment formed by the node D and the additional node add1 both do notpass through the barrier region, such as the barrier region 212 and thebuffer region 214, and j2≠5, the node C and the additional node add1 areused as third navigation nodes and are added to the third navigationnode set S3. set j1=j1+1=1, j2=j2+1=2, and the method returns to step(2′), and a plurality of second navigation nodes and the additional nodesubsequently obtained are used as third navigation nodes and are addedto the third navigation node set S3.

In some variations of the embodiments of the invention, set j1=0, j2=1,designation variable p=0, the quantity of second navigation nodes in thesecond navigation node set S2 be denoted by q (q=7 in the presentembodiment), C=b₀, D=b₁, the X coordinate add.x of the additional nodeadd be the X coordinate D.x of the node D, and the Y coordinate add.y ofthe additional node add be the Y coordinate C.y of the node C. Thus, theadditional node add2 is obtained. If at least one of the line segmentsformed by the nodes C and D and the additional node add2 passes throughthe barrier region, such as the barrier region 212 and the buffer region214, set designation variable p=p+1, meanwhile p=1, set the firstcoordinate add.x of the additional node add be the first coordinate C.xof the node C, and the second coordinate add.y of the additional nodeadd be the second coordinate D.y of the node D to obtain the additionalnode add1, and the method returns to step (4′), whether the line segmentformed by the add1 and the nodes C and D passes through the barrierregion 212 and the buffer region 214 is determined. If at least one ofthe line segments formed by the nodes C and D and the additional nodeadd1 passes through the barrier region, such as the barrier region 212and the buffer region 214, set designation variable p=p+1, meanwhile,p=2, and the quantity of second navigation nodes in S2 set as q=q+1.That is, set the quantity of second navigation nodes in S2 be 8, and thecoordinate of b₄ is assigned to b₅, the coordinate of b₃ is assigned tob₄, until the coordinate of b₁ is assigned to b₂ by the same analogy.Then, set the coordinate of b₁ be the middle point between b₀ (the nodeC) and b₁ (the node D). That is, the middle point between b₀ and b₁ isalso used as a second navigation node and is added to the secondnavigation node set, and set p=0, and whether the connection lineconnecting the middle point and b₀ and the connection line connectingthe additional node add and the middle point and b₀ pass through thebarrier region is determined by using the above steps.

Thus, a plurality of third navigation nodes can be obtained using thealgorithm to form the third navigation path 230 as indicated in FIG. 7.Every two adjacent line segments in the third navigation path 230 areorthogonal to each other. In step S150: the AGV is navigated to thetarget position using the third navigation path 230.

Some optimization methods of the environment map provided in theinvention are described below with reference to FIG. 8 to FIG. 10.

Specifically, the environment map 301, which can be realized by a dotmatrix map, is composed of a plurality of pixel points. The environmentmap 301 includes an open region 311 composed of a plurality of pixelpoints displaying white color, that is, the first color, and a barrierregion 312 composed of a plurality of pixel points displaying blackcolor, that is, the second color. In some embodiments, for any pixelpoint of the environment map, the pixel point displays the first colorif the pixel point displays black color, and the eight pixel pointsadjacent to the pixel point, such as four pixel points located on thetop, the bottom, the left and the right of the pixel point, and fourpixel points located on the two diagonal lines, display white color.

In some embodiments, for any pixel point of the environment map, a pixelpoint displays the same color with at least five consecutive pixelpoints of the eight pixel points surrounding the pixel point if the atleast five consecutive pixel points display a color different from thatdisplayed by the pixel point. For example, if the pixel point displayswhite color, and five of the eight pixel points surrounding the pixelpoint display black color, the pixel point displays black color. Thefive pixel points refer to the pixel points at the top, the top left,the left, the bottom left and the bottom of the pixel point.

Referring to FIG. 8, a schematic diagram of a pre-optimized environmentmap according to an embodiment of the invention is shown. As indicatedin FIG. 8, for any of the barrier region 312 in the environment map 301,the serrated region is filled up with black color if the barrier region312 has a serrated edge. Specifically, for any of the barrier region312, the connection line connecting the two and more than two pixelpoints is filled up with black color if the edge of the barrier region312 has two and more than two pixel points displaying white color.

In some embodiments, a barrier region 312 of the environment map 301 hasa corner area. If the corner area of the barrier region 312 has two andmore than two pixel points displaying white color, and the edge of thebarrier region 312 has two and more than two pixel points displayingwhite color and located in the same column or the same row with the twoand more than two pixel points displaying white color, the connectionline connecting the pixel points displaying white color is filled withblack color. As indicated in FIG. 8, the corner area C of the barrierregion 312 has two and more than two pixel points displaying whitecolor; that is, the pixel points displaying white color and located tothe right of the area C of the barrier region 312, and the edge of thebarrier region 312 has two and more than two pixel points displayingwhite color and located in the same column or the same row of the arrayof pixel points with two and more than two pixel points displaying whitecolor and located at the area C. As shown in the area D, the pixelpoints displaying white color located to the right of the area D of thebarrier region 312, such that the connection line connecting the twopixel points of the areas C and D, which are most farther away from eachother and display white color, is displayed in black color so that allpixel points on the connection line display black color. In the presentembodiment, the pixel points, which are located at the areas C and D anddisplay white color, are located in the same row in the array of pixelpoints.

Referring to FIG. 10, a schematic diagram of a barrier region accordingto an embodiment of the invention is shown. As indicated in FIG. 10, forany of the barrier region of the environment map 312, if three of theeight pixel points adjacent to a pixel point 316 displaying while colorare now displaying black color on the edge of the barrier region 312,the pixel point 316 originally displaying white color changes to displayblack color.

Referring to FIG. 9, a schematic diagram of an optimized environment mapaccording to an embodiment of the invention is shown. By performingoptimization to the environment map using one of many of the aboveoptimization methods, the noises contained in the environment map arereduced, and the edges of the barrier region are modified. The optimizedenvironment map 302 can be obtained with reference to FIG. 9. Theinvention generate a navigation path according to the optimizedenvironment map 302, and the influence on the navigation path caused bythe noises and the serration on the edges of the barrier region isreduced.

In comparison to the prior art, the invention has following advantages:

1) By performing optimization to the navigation path twice, every twoadjacent line segments in the third navigation path are orthogonal toeach other, and the quantity of turns in the navigation path of theautomated guided vehicle is reduced;

2) By optimizing the first navigation path with the dichotomy method andorthogonalizing the second navigation path, the quantity of nodes in thenavigation path is reduced;

3) By performing optimization to the environment map, the noisescontained in the environment map are reduced, the edges of the barrierregion are modified, and the influence on the planning of navigationpath caused by the noises is reduced.

While the invention has been described by way of example and in terms ofthe preferred embodiment(s), it is to be understood that the inventionis not limited thereto. On the contrary, it is intended to cover variousmodifications and similar arrangements and procedures, and the scope ofthe appended claims therefore should be accorded the broadestinterpretation so as to encompass all such modifications and similararrangements and procedures.

What is claimed is:
 1. A method for navigating an automated guidedvehicle, comprising: generating an environment map for the automatedguided vehicle and setting a target position, wherein the environmentmap at least comprises an open region and a barrier region; generating afirst navigation path on the environment map according to the targetposition; optimizing the first navigation path by using a dichotomymethod to generate a second navigation path; orthogonalizing the secondnavigation path to generate a third navigation path, wherein every twoadjacent line segments in the third navigation path are orthogonal toeach other; and navigating the automated guided vehicle to the targetposition by using the third navigation path.
 2. The method according toclaim 1, wherein the first navigation path comprises a plurality offirst navigation nodes, and the step of optimizing the first navigationpath by using the dichotomy method to generate second navigation pathcomprises: selecting two first navigation nodes by using the dichotomymethod, and determining whether the connection line connecting the twofirst navigation nodes passes through the barrier region, and furtherselecting a plurality of second navigation nodes from a plurality of thefirst navigation nodes to form the second navigation path, wherein aquantity of the second navigation nodes is smaller than or equal to aquantity of the first navigation nodes.
 3. The method according to claim2, wherein a plurality of first navigation nodes a_(0˜)a_(n−1) form afirst navigation node set S1={a₀, a₁, a₂ . . . a_(n−1)}, wherein n is aninteger greater than or equal to 1, and the step of optimizing the firstnavigation path by using the dichotomy method to generate the secondnavigation path comprises: i. setting k1=0, k2=n−1; ii. settingA=a_(k1), B=a_(k2), wherein nodes A and B are two nodes selected fromthe first navigation node set, and k1 and k2 respectively indicate thetwo first navigation nodes in the first navigation node set thatcorrespond to the nodes A and B; iii. determining whether the linesegment formed by the nodes A and B passes through the barrier region;if the line segment formed by the nodes A and B passes through thebarrier region, setting k2=(k1+k2)/2 and rounding k2, and returning tostep ii; if the line segment formed by the nodes A and B does not passthrough the barrier region, and k2≠n−1, taking the node A as a secondnavigation node and adding the node A to a second navigation node setS2, setting k1=k2, k2=n−1, and returning to step ii; and if the linesegment formed by the nodes A and B does not pass through the barrierregion, and k2=n−1, taking the nodes A and B as second navigation nodesand adding the nodes A and B to the second navigation node set S2; andiv. obtaining the second navigation node set S2, wherein a plurality ofthe second navigation nodes in the second navigation node set S2 formthe second navigation path.
 4. The method according to claim 1, whereinthe second navigation path comprises a plurality of second navigationnodes, and the step of orthogonalizing the second navigation path togenerate a third navigation path comprises: forming an additional nodewith respect to every two of the adjacent second navigation nodes,wherein the connection lines connecting the additional node and the twoadjacent second navigation nodes are parallel to the first direction orthe second direction, and the first direction is perpendicular to thesecond direction; and using the additional node and at least some of thesecond navigation nodes as third navigation nodes, wherein a pluralityof the third navigation nodes form the third navigation path.
 5. Themethod according to claim 4, wherein a plurality of the secondnavigation nodes b₀-b_(m−1) form the second navigation node set S2={b₀,b₁, b₂ . . . b_(m−1)}, wherein m is an integer greater than or equal to1, each of the second and third navigation nodes has a first coordinatealong the first direction and a second coordinate along the seconddirection, wherein the step of orthogonalizing the second navigationpath to generate the third navigation path comprises: i′. setting j1=0,j2=1, wherein a variable p=0 is designated, and quantity of the secondnavigation nodes in the second navigation node set S2 is denoted by q;ii′. setting C=b_(j1), D=b_(j2), wherein nodes C and D are two nodesselected from the second navigation node set, and j1 and j2 respectivelyindicate the two second navigation nodes in the second navigation nodeset that correspond to the nodes C and D; iii′. setting a firstcoordinate of the additional node be a first coordinate of the node C,and a second coordinate of the additional node add be a secondcoordinate of the node D; iv′. respectively determining whether the linesegments formed by the nodes C and D and the additional node passthrough the barrier region; if the line segments formed by the nodes Cand D and the additional node both do not pass through the barrierregion, and j2≠m−1, taking the node C and the additional node as thethird navigation nodes for being added to a third navigation node setS3, setting j1=j1+1, j2=j2+1, and the method returning to step ii′; ifj2=m−1, taking the nodes C and D and the additional node as the thirdnavigation nodes for being added to the third navigation node set S3; ifat least one of the line segments formed by the nodes C and D and theadditional node passes through the barrier region, setting p=p+1, whenp=1, setting the first coordinate of the additional node being a firstcoordinate of the node D, and the second coordinate of the additionalnode being a second coordinate of the node C, and returning to step iv′;and when p=2, setting b_(q)=b_(q−1), b_(q−1)=b_(q−2) . . .b_(j2+1)=b_(j2), b_(j2).x=(C.x+D.x)/2, b_(j2).y=(C.y+D.y)/2, q=q+1, p=0,and returning to step iii′, wherein b_(j2).x is a first coordinate ofb_(j2); b_(j2).y is a second coordinate of b_(j2); C.x is the firstcoordinate of the node C; C.y is the second coordinate of the node C;D.x is the first coordinate of the node D; and D.y is the secondcoordinate of the node D; and v′. obtaining the third navigation nodeset S3, wherein a plurality of the third navigation nodes in the thirdnavigation node set S3 form the third navigation path.
 6. The methodaccording to claim 1, wherein the environment map comprises an openregion composed of a plurality of pixel points displaying a first color,and the barrier region composed of a plurality of pixel pointsdisplaying a second color, wherein the step of generating theenvironment map for the automated guided vehicle and setting the targetposition comprises: optimizing the environment map by changing the colordisplayed by some of the pixel points according to each pixel point andits surrounding pixel points of the environment map.
 7. The methodaccording to claim 6, wherein the step of optimizing the environment mapcomprises: for any of the pixel points of the environment map, enablingthe any pixel point to display in the first color if the any pixel pointoriginally displays the second color but a plurality of the pixel pointsadjacent to the pixel point display the first color.
 8. The methodaccording to claim 7, wherein the step of optimizing the environment mapcomprises: for any of the pixel points of the environment map, enablingthe any pixel point to display the same color with at least fiveconsecutive pixel points of the eight pixel points surrounding the anypixel point if the at least five consecutive pixel points display acolor different from that displayed by the any pixel point.
 9. Themethod according to claim 6, wherein the step of optimizing theenvironment map comprises: for any of the barrier region of theenvironment map, filling up a serrated region with the second color ifthe any of the barrier region has an edge being serrated.
 10. The methodaccording to claim 9, wherein the step of optimizing the environment mapcomprises: for any of the barrier region of the environment map, if theedge of the barrier region has two and more than two of the pixel pointsdisplaying the first color, filling up a connection line connecting thetwo and more than two pixel points with the second color.
 11. The methodaccording to claim 6, wherein the step of optimizing the environment mapcomprises: if a corner area of the barrier region of the environment maphas two and more than two pixel points displaying the first color, andan edge of the barrier region has two and more than two pixel pointsdisplaying the first color and located in the same column or the samerow with the two and more than two pixel points displaying the firstcolor in the corner area, filling up a connection line connecting thepixel points originally displaying the first color with the secondcolor.
 12. The method according to claim 6, wherein the step ofoptimizing the environment map comprises: for any of the barrier regionof the environment map, enabling the pixel point originally displayingthe first color to change to display the second color if three of eightpixel points adjacent to the pixel point displaying the first color aredisplaying the second color on an edge of the barrier region.